Quantum technologies

During my time at the 1D experiment, we modified the Raman laser setup with an AOM, supplementary optics and control circuitry to allow us to produce fast Raman pulses. We have successfully demonstrated our ability to induce Rabi oscillations in a sample of Caesium atoms with Rabi frequencies up to 1.4 MHz. We have put this to use to develop a new method to measure the radial temperature in our optical lattice setup and perform Ramsey interferometry. The temperature measurement made use of the Gaussian intensity distribution of the Raman laser beams addressing the atoms and of the subsequent differences in induced Rabi frequency over the trapped atoms. We were able to model the behaviour and extract the radial temperature at laser powers of up to 1 mW per Raman beam.
We performed Ramsey interferometry with the new system, using a Keysight FPGA for the phase modulation of the π/2 pulses. The new hardware was integrated into the existing experimental sequences and it provides the opportunity to further simplify the setup since three of its output channels are still unused. The Mandelstam-Tamm speed limit was probed by measuring the evolution of the wave function from its initial to an orthogonal state. This measurement was done by performing Ramsey interferometry with an additional lattice shift between the two characteristic π/2 pulses. We verified the validity of the quantum speed limit through our measurements, which showed for trap depths of 14.286 μK, 28.689 μK and 57.813 μK that the evolution time was slower than the limit predicted through calculation.

The content of this thesis will be divided into 3 parts. In the first chapter, I will go over the theory behind the optical lattice setup, how the experiment is designed and the necessary steps towards an experiment-ready atom sample. I will also cover the derivation of the quantum speed limit. The second chapter will treat the design, operation and calibration of the Raman laser setup, which was modified to perform fast pulses, phase modulation of these pulses and ultimately Ramsey interferometry. The third chapter treats the experiments performed with the aforementioned laser setup, the results and analysis. At the end, I will give a short summary and an outlook on the next possible steps to take with the working setup and which further experiments might be performed.